Mr Herrick has stepped down from his post as chief financial officer with immediate effect, but will not leave the company formally until February 7.
There was no reason given for his departure, but the move comes after Debenhams warned on Tuesday that profits were expected to fall by as much as 26% due to its failure to entice a rush of shoppers in the days leading up to Christmas, sparking a 12% shares slide.
It also follows reports last week that Mr Herrick's position at the group was under pressure amid shareholder concern over his performance.
He has been criticised over a so-called "Santa tax" letter hitting suppliers with demands for discounts days before Christmas.
Investors are also said to have been angered by guidance provided to analysts this year, with the City caught off guard by an earlier profits warning in March and unexpected costs revealed when full-year results were announced in October.
Debenhams said it had begun a search to find Mr Herrick's replacement, with finance director Neil Kennedy taking on the role on an interim basis.
Mr Herrick will continue to be paid salary and benefits worth nearly £490,000 over a 12-month notice period, with up to £12,000 on top to cover legal fees.
Debenhams said earlier this week that half-year pre-tax profits were expected to fall to around £85 million from £114.7 million the year before, after discounting ate into a dismal 0.1% like-for-like sales increase for the 17 weeks to December 28.
The hoped-for sales surge in the last week before Christmas failed to materialise and the group said it would have to resort to more discounting in January and February to clear stock.
It was the group's second profits warning in less than a year, with poor trading at the start of 2013 seeing profits fall 2.7% to £154 million for the 12 months to August 31.
But Debenhams chief executive Michael Sharp insisted on Tuesday the chain was battling against an "extremely difficult environment" that led many retailers to slash prices in the festive run up.
The group also blamed bad weather for having an impact on clothing sales, which fell over the 17-week period.
But rivals John Lewis and House of Fraser have reported buoyant trading over the period, which is likely to increase pressure on Mr Sharp.
John Lewis said like-for-like sales climbed 6.9% over the five weeks to December 28, while House of Fraser hailed its best ever Christmas with comparable store sales up 7.3%.
Mr Herrick's departure comes after just two years in the role.
Mr Sharp said: "On behalf of the board, I would like to thank Simon for his hard work and contribution over the past two years.
"We wish him well in the future."